Citizen science is progressive in science, as it removes biases that get placed into high-level research.

Citizen science speeds up discoveries.

These projects help out the participants in their lives to gain scientific skills

Citizen science projects put critical data and collection in the hands of amateurs. It is hard enough to control for spurious variables in a well-controlled research setting. Thinking that crowd-sourcing will deliver reliable data is wishful thinking at best, a Pollyanna distraction to serious scientific inquiry at worst.

Some citizen science projects might be unethical.

Citizen scientists can only make contributions which require little skill or training, limiting their usefulness too much to be truly beneficial.

There are activities with a greater benefit to science than citizen science. If citizen science is pursued instead, it can be a drawback to someone's potential in helping science.

Citizen science can create so much information that real and more valuable discoveries may get lost in the wealth and buzz of it.